Semiconductor transistors, in particular field-effect controlled switching devices such as a Metal Oxide Semiconductor Field Effect Transistor (MOSFET) or an Insulated Gate Bipolar Transistor (IGBT), have been used for various applications including but not limited to use as switches in power supplies and power converters, electric cars, air-conditioners, and even stereo systems. Particularly with regard to power devices capable of switching large currents and/or operating at higher voltages, a low on-state resistance Ron and high breakdown voltages Ubd are often desired.
To achieve low on-state resistance Ron and high breakdown voltages Ubd, charge-compensation semiconductor devices were developed. The compensation principle is based on a mutual compensation of charges in n- and p-doped regions, which are often also referred to as n- and p-doped pillar regions, in the drift zone of a vertical MOSFET.
Typically, the charge-compensation structure formed by p-type and n-type regions is arranged below the actual MOSFET-structure, with its source, body regions and gate regions, and also below the associated MOS-channels that are arranged next to one another in the semiconductor volume of the semiconductor device or interleaved with one another in such a way that, in the off-state, their charges can be mutually depleted and that, in the activated state or on-state, there results an uninterrupted, low-impedance conduction path from a source electrode near the surface to a drain electrode arranged on the back side.
By virtue of the compensation of the p-type and n-type dopings, the doping of the current-carrying region can be significantly increased in the case of compensation components, which results in a significant reduction of the on-state resistance Ron despite the loss of a current-carrying area. The reduction of the on-state resistance Ron of such semiconductor power devices is associated with a reduction of the heat generated by the current in the on-state, so that such semiconductor power devices with charge-compensation structure remain “cool” compared with conventional semiconductor power devices.
Voltage converters typically employ field-effect transistors, in particular MOSFETs or IGBTs. Such voltage converters may e.g. convert a voltage from a common alternating voltage mains network to a direct voltage required for operating an electronic device at a low voltage e.g. in a range of 12 V or 48V down to below 1 V.
In hard on- and off-switching applications of power MOSFETs, in particular at higher current densities, oscillating transient values of the gate and drain voltages may be generated, so-called “ringing”. Ringing effects refer to oscillations of gate and drain voltages, and are typically caused by parasitics of the switching circuitries, in particular source inductivities. With the often desired miniaturization of power MOSFETs, ringing effects may become more severe.
Accordingly, there is a need to improve field-effect semiconductor devices, in particular power field-effect semiconductor devices including charge-compensation field-effect semiconductor devices and manufacturing of those semiconductor devices.